Apex domains cannot have CNAME records.
Question and response
Question
dig localdns.co.za. NS
Answer
localdns.co.za. 4 NS linus.ns.1-grid.net.
localdns.co.za. 4 NS linus.ns.1-grid.co.uk.
localdns.co.za. 4 NS linus.ns.1-grid.co.za.
localdns.co.za. 4 NS linus.ns.1-grid.com.
Authority
The response has no authority records.
Additional
linus.ns.1-grid.co.uk. 2 A 41.185.8.21
linus.ns.1-grid.co.za. 2 A 41.185.8.22
linus.ns.1-grid.com. 2 A 41.185.8.21
linus.ns.1-grid.net. 2 A 41.185.8.22
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0